Torque wrench

ABSTRACT

This invention relates to torque wrenches, and more particularly to torque wrenches that are bi-directional in operation. A torque wrench comprises a housing in which is mounted a rotatable ratchet mechanism, a first lever and a first drive for applying a driving force to the first lever to pivot the first lever reciprocatingly between a rest position and a fully displaced position. Further included is a second lever and second drive for applying a driving force to the second lever to pivot the second lever reciprocatingly between a rest position and a fully displaced position.

TECHNICAL FIELD

This invention relates to torque wrenches, and more particularly totorque wrenches that are bi-directional in operation.

BACKGROUND ART

Torque wrenches, and in particular hydraulic torque wrenches, are wellestablished for use in tightening bolted joints. Such wrenches usuallyinclude a hydraulically-operated ram reciprocation of the piston ofwhich causes rotation of an associated crank lever. A ratchet mechanismincorporating means for co-operation with the nut or bolt to betightened is, in turn, rotated by the lever through drive means reactingbetween the lever and the ratchet mechanism whereby the nut or bolt isitself rotated.

The application of such a torque wrench to the nut or bolt provides forrotation of the nut or bolt in one direction.

In order to rotate the nut or bolt in the opposite direction, the wrenchmust be removed from the nut or bolt, turned over, and re-applied to thenut or bolt.

There are situations, for example in the subsea and nuclear industries,where torque wrenches have to be operated remotely, and, in suchcircumstances, it is not feasible to remove, turn over and reapply thetorque wrench to enable the nuts or bolts to be rotated in differentdirections.

Additionally, torque wrenches are finding uses in many industries asvalve actuators where rotation of the valve spindle in both directionsmust be readily available.

It has therefore been proposed, for example as disclosed in U.S. Pat.No. 2,729,997, to provide torque wrenches incorporating bi-directionalmechanisms whereby rotation in both directions can be achieved withoutremoving the wrench from the component to be rotated.

Such bi-directional torque wrenches commonly incorporate a pair of driveshoes each reacting between the crank lever and the ratchet mechanism,one shoe associated with clockwise rotation of the ratchet mechanism andthe other shoe associated with anticlockwise rotation of said mechanism.

More particularly, the two drive shoes are interconnected with oneanother, each shoe being movable between an operative drive positionengaging with the ratchet mechanism and an inoperative positiondisengaged from said mechanism. The interconnection of the two shoes issuch that, when one of the drive shoes is in its operative driveposition, the other drive shoe is completely disengaged from the ratchetmechanism.

A switching mechanism, which may be manually operated or powered, isprovided to alter the relative positions of the drive shoes to achieveeither clockwise or anticlockwise rotation. Failure to disengage one ofthe drive shoes when engaging the other shoe will result in the wrenchlocking up and preventing rotation of the ratchet mechanism in eitherdirection--the drive shoes will work against one another when bothengage the ratchet mechanism.

In the aforementioned subsea and nuclear industries, it is clearly notpossible to switch the torque wrench manually, and a remote controlarrangement is therefore required.

However, remote switching mechanisms are both expensive and complex toinstall. For example the wrench may incorporate a hydraulically-operatedram to effect the switching which must be provided with a receiver and apower supply actuated by a remote signal.

Such additional equipment clearly increases the risk of a failureoccurring, while the remote nature of the switching operation leads toquestions as to whether or not switching has in fact occurred. A sensorcould be provided to detect the appropriate movement, but this addsstill further to the cost.

DISCLOSURE OF THE INVENTION

It would be desirable to be able to provide a torque wrench capable ofproviding both clockwise and anticlockwise rotation of a componentwithout the necessity of removing the wrench from the component andwithout the requirement for a manually-operated or powered switchingmechanism within the wrench.

According to the present invention there is provided a torque wrenchcomprising a housing in which is mounted a rotatable ratchet mechanismadapted to cooperate with a component to be rotated by the wrench, afirst drive lever extending radially of said ratchet mechanism andpivotal about one end thereof coaxial with the ratchet mechanism, firstlever drive means for applying a driving force to the other end of thefirst lever to pivot said first lever about the one end thereofreciprocatingly between a rest position and a fully displaced position,first drive means reacting between the first lever and the ratchetmechanism whereby, on movement of the first lever from the rest positiontowards the fully displaced position, the ratchet mechanism is rotatedin one direction, a second drive lever extending radially of saidratchet mechanism and pivotal about one end thereof coaxial with theratchet mechanism, second lever drive means for applying a driving forceto the other end of the second lever to pivot said second lever aboutthe one end thereof reciprocatingly between a rest position and a fullydisplaced position, and second drive means reacting between the secondlever and the ratchet mechanism whereby, on movement of the second leverfrom the rest position towards the fully displaced position, the ratchetmechanism is rotated in the other direction, the wrench furthercomprising control means reacting between the housing and the first andsecond drive means such that, with a lever in its rest position, theassociated drive means is disengaged from the ratchet mechanism, andsuch that, on movement of a drive lever from its rest position towardsits fully displaced position, the associated drive means are broughtinto engagement with the ratchet mechanism while the other drive leveris held in its rest position with its associated drive means disengagedfrom the ratchet mechanism.

It will thus be appreciated that, with such an arrangement, rotation ofthe component to be tightened or loosened can be achieved in eitherdirection by appropriate pivoting movement of the associated drivelever, there being no need to actuate any switching means, disengagementof the non-active drive means occurring automatically when in its restposition by virtue of said control means.

In one embodiment of the invention, each drive means is mounted on alever arm pivotal on the associated drive lever, abutment means beingprovided on the housing whereby, with the drive lever in its restposition, the lever arm engages the associated abutment means to pivotthe drive means out of engagement with the ratchet mechanism, and, onmovement of the drive lever to a displaced position, the lever armdisengages from said abutment means whereby the drive means move intodriving engagement with the ratchet mechanism.

In an alternative embodiment of the invention, the torque wrenchincludes, for each drive lever, a lever arm pivotal on the housing, oneend of the lever arm being-adapted for engagement with the associateddrive means and the other end of the lever arm being adapted forengagement by abutment means on the associated drive lever, thearrangement being such that, with the drive lever in its rest position,the abutment means on the drive lever engage the other end of the leverarm to pivot said lever arm whereby the one end thereof disengages thedrive means from the ratchet mechanism, and, on movement of the drivelever to a displaced position, the other end of the lever arm disengagesfrom the abutment means and the drive means move into driving engagementwith the ratchet mechanism.

Preferably the lever drive means each comprise a fluid-operatedpiston-cylinder assembly interconnected with the other end of theassociated drive lever, extension of the piston of the assembly causingpivotal movement of the associated drive lever about the one end thereoffrom its rest position towards its fully displaced position.

The fluid supply to said piston-cylinder assemblies is preferably suchthat, prior to extension of the piston of one assembly to move theassociated drive lever from its rest position, the piston of the otherassembly is fully retracted to hold the associated drive lever in itsrest position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show parts of two alternative torque wrenches according tothe invention, while FIG. 1' shows an enlargement of the engagement ofthe left drive shoe and ratchet mechanism of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, there is illustrated part of a bi-directionaltorque wrench including a housing part of which is shown at 2. Thehousing 2 contains a ratchet mechanism 4 rotatable within the housingabout point P and provided with a hexagonal recess 6 therein forco-operation with a nut, bolt or socket to be rotated.

A first drive lever or crank 8 for the mechanism 4 has one end pivotalabout the point P, the piston rod 10 of a first hydraulicpiston-cylinder assembly 12 being pivotally attached at 14 to the otherend of said lever 8.

The lever 8 is shown in its rest position with the piston rod 10 of theassembly 12 fully retracted. On extension of the rod 10, the lever 8 ispivoted about the point P in an anticlockwise direction towards a fullydisplaced position as will be detailed below.

A second drive lever or crank 16 for the mechanism 4 has one end pivotalabout the point P, the piston rod 18 of a second hydraulicpiston-cylinder assembly 20 being pivotally attached at 22 to the otherend of the lever 16. The assemblies 12,20 work in opposite directions toone another.

The lever 16 is shown in a displaced position with the piston rod 18 ofthe assembly 20 partly extended and having pivoted the lever 16 in aclockwise direction from its rest position.

Drive means react between the levers 8,16 and the ratchet mechanism 4 toenable appropriate rotation of said mechanism on pivotal movement of thelevers 8,16 about the point P.

More particularly, a carrier arm 24 is pivotally mounted at 26 on thelever 8, one end of said arm 24, with the lever 8 in its illustratedrest position, engaging an abutment 28 within the housing 2 whereby thearm 24 is held in the inoperative position shown in the drawing.

A toothed drive shoe 30 is carried on the other end of said arm 24, saidshoe 30, with the arm 24 in its inoperative position, being held out ofengagement with the teeth of the ratchet mechanism 4.

The arrangement is such that, on extension of the piston rod 10 of theassembly 12 from its fully retracted position, the lever 8 is pivoted inan anticlockwise direction from its illustrated rest position. The oneend of the carrier arm 24 is thereby disengaged from the abutment 28 andpivots in an anticlockwise direction about the point 26 whereby theteeth of the drive shoe 30 are wedged into meshing engagement with theteeth of the ratchet mechanism 4, continued pivotal movement of thelever 8 resulting in corresponding anticlockwise rotation of themechanism 4.

A corresponding drive arrangement is provided between the lever 16 andthe mechanism 4, with components equivalent to those of the arrangementbetween the lever 8 and the mechanism 4 being similarly referenced butwith a dash added.

As the lever 16 is displaced from its rest position, the carrier arm 24¹has disengaged from the abutment 28¹ and the drive shoe 30¹ has wedgedinto driving engagement with the ratchet mechanism 4.

As shown in an enlarged scale in FIG. 1', drive shoe 30' experiences acircumferential force F at the initiation of a clockwise movement ofcrank 16 transmitted by wall 32 of cavity 34, and drive shoe 30' opposesthis with a force F⁻. The components of force F⁻ include a perpendicularcomponent directed against wall 32 and a parallel component directedparallel to wall 32. The parallel component of force F⁻ thus serves topush drive shoe 30' into engagement with the teeth of ratchet mechanism4. Once engaged by the teeth of ratchet mechanism 4, continued clockwisemovement of crank 16 causes the teeth of ratchet mechanism 4 to produceanother (counter) force acting to push drive shoe 30' out of engagementwith the teeth of ratchet mechanism 4. However, as shown by shaded areas36 of the teeth of drive shoe 30', areas 36 are trapped (relative to theonly direction of movement possible for drive shoe 30' which is parallelto wall 32) below the corresponding portion of the meshing teeth ofratchet mechanism 4. Drive shoe 30' is thus trapped or wedged inposition during further clockwise movement of crank 16, even thoughcontinued movement of crank 16 causes the teeth of ratchet mechanism 4to react against the teeth of drive shoe 30' with the force acting tomove drive shoe 30' out of engagement with the teeth of ratchetmechanism 4. Drive shoe 30' is thus wedged in place so long as crank 16continues the clockwise movement.

When crank 16 reverses movement, the first (small) initial reverse orcounterclockwise movement of crank 16 occurs without engagement of wall38 and drive shoe 30' due to the gap between drive shoe 30' and wall 38of cavity 34,. When the reverse movement of crank 16 exceeds the gapdistance and thus does cause engagement of wall 38 and drive shoe 30',the gap is now located between drive shoe 30' and wall 32. This gapalong wall 32 is sufficient in size to allow areas 36 to clear thecorresponding portions of the teeth of ratchet mechanism 4 as drive shoe30' is constrained to move parallel to wall 32. The escape of the teethof drive shoe 30' from the teeth of ratchet mechanism is facilitatedboth by the opposite force direction of the components (forces F and F⁻are now oppositely directed or reversed on wall 38, as are thecomponents and particularly the component parallel to wall 38 which nowis directed outwards) as well as by the action of the teeth of ratchetmechanism which continue to push the teeth of drive shoe 30' awaytherefrom (no matter what the direction of rotation of drive shoe 30').

When the counterclockwise movement of crank 16 is completed and afurther movement of drive shoe 30' is desired, the first (small) initialclockwise movement crank 16 results in drive shoe 30' being releasedfrom the out of engagement position (as shown by drive shoe 30 inFIG. 1) and inwards towards the teeth of ratchet mechanism 4. When theinward clockwise corners of the tips of the teeth of drive shoe 30'first encounter the outward counterclockwise comers of the tips of theteeth of ratchet mechanism 4 (perhaps after the tops of both sets ofteeth ride along one another), the downward force component as well asthe complementary shapes of the teeth cause the teeth of drive shoe 30'to immediately move into engagement with the teeth of ratchet mechanism4. Once engagement is achieved, further clockwise movement crank 16 thenkeeps areas 36 trapped in place to complete the next drive cycle ofratchet mechanism 4.

With both the clockwise and anticlockwise drive arrangements, movementof the piston rod 10,18 to its fully retracted position as the driveshoes 30, 30' ride up and over the teeth of ratchet mechanism 4, bringsthe one end of the associated lever arm 24,24¹ into engagement with theabutment 28,28¹ on the housing to pivot said lever arm 24,24¹ about thepoint 26,26¹ into its inoperative position and to disengage the driveshoe 30,30¹ from the ratchet mechanism 4.

The hydraulic supply to the assemblies 12,20 is such that, on demand toone of said assemblies for extension purposes, the fluid is first of allfed to the other assembly to ensure that the associated piston rod isfully retracted and thereby that the associated drive shoe is disengagedfrom the ratchet mechanism 4.

So, on driving of the ratchet mechanism 4 in one direction by the shoe30,30¹, the other shoe 30¹,30 is totally disengaged from the mechanism,thereby avoiding any locking up of said mechanism.

FIG. 2 illustrates an alternative arrangement for engaging anddisengaging the drive shoes with and from the ratchet mechanism.Components equivalent to those of FIG. 1 are similarly referenced.

Effectively, the locations of the lever arms 24,24¹ are pivotallymounted on the housing 2. With the lever 8,16 in its rest position, theone end of the lever arm 24,24¹ engages the associated abutment 28,28¹whereby the other end of the lever arm 24,24¹ is pivoted upwardly toengage the drive shoe 30,30¹ and lift it out of engagement with theratchet mechanism 4 (as shown for shoe 30 in FIG. 2).

Pivoting movement of the lever 8,16 from its rest position towards adisplaced position results in disengagement of the one end of the leverarm 24,24¹ from the abutment 28,28¹ and downward pivoting movement ofthe other end of the lever arm 24,24¹ out of contact with the drive shoe30,30¹ whereby said shoe 30,30¹ moves into meshing engagement with theratchet mechanism 4 (as is shown for shoe 30¹ in FIG. 2).

Thus there is provided a bi-directional torque wrench which isparticularly suited to remote operation, for example in subsea andnuclear applications, in that there is no need to provide separateswitching of the drive means when moving from clockwise to anticlockwiserotation and vice versa. Location of a drive lever 8,16 in its restposition ensures that the associated drive shoe is totally disengagedfrom the ratchet mechanism, and thereby enables rotation of themechanism 4 by the other drive lever 16,8 without the possibility ofmalfunctioning of the wrench.

Clearly the precise means by which a drive shoe is disengaged from theratchet mechanism 4 can vary from those illustrated, providing saiddisengagement is achieved when the lever is in its rest position.

I claim:
 1. A torque wrench comprising a housing (2) in which is mounteda rotatable ratchet mechanism (4) adapted to co-operate with a componentto be rotated by the wrench, a first drive lever (8) extending radiallyof said ratchet mechanism and pivotal about one end thereof coaxial withthe ratchet mechanism (4), first lever drive means (12) for applying adriving force to the other end of the first lever (8) to pivot saidfirst lever (8) about the one end thereof reciprocatingly between a restposition and a fully displaced position, first drive means (30) reactingbetween the first lever (8) and the ratchet mechanism (4) whereby, onmovement of the first lever (8) from the rest position towards the fullydisplaced position, the ratchet mechanism (4) is rotated in onedirection, a second drive lever (16) extending radially of said ratchetmechanism (4) and pivotal about one end thereof coaxial with the ratchetmechanism (4), second lever drive means (20) for applying a drivingforce to the other end of the second lever (16) to pivot said secondlever (16) about the one end thereof reciprocatingly between a restposition and a fully displaced position, and second drive means (30¹)reacting between the second lever (16) and the ratchet mechanism (4)whereby, on movement of the second lever (16) from the rest positiontowards the fully displaced position, the ratchet mechanism (4) isrotated in the other direction, characterised by a control means (24,26, 28; 24¹, 26¹, 28¹) for controlling an interaction between thehousing (2) and the first and second drive means (30, 30¹) such that,with a lever (8, 16) in its rest position, the associated drive means(30, 30¹) is disengaged from the ratchet mechanism (4), and such that,on movement of a drive lever (8, 16) from its rest position towards itsfully displaced position, the associated drive means (30, 30¹) isbrought into engagement with the ratchet mechanism (4) while the otherdrive lever (16,8) is held in its rest position with its associateddrive means (30¹, 30) disengaged from the ratchet mechanism (4).
 2. Atorque wrench as claimed in claim 1 in which each drive means (30, 30¹)is mounted on a lever arm (24, 24¹) pivotal on the associated drivelever (8, 16), an abutment means (28, 28¹) being providing on thehousing (2) (a) for engaging, with the drive lever (8, 16) in its restposition, the arm lever (24, 24¹) with the associated abutment means(28, 28¹) to pivot the drive means (30, 30¹) out of engagement with theratchet mechanism (4), and, (b) for disengaging on movement of the drivelever (8, 16) to a displaced position, the lever arm (24, 24¹) from saidabutment means (28, 28¹) whereby the drive means (30, 30¹) move intodriving engagement with the ratchet mechanism (4).
 3. A torque wrench asclaimed in claim 1 and including, for each drive lever (8, 16), a leverarm (24, 24¹) pivotal on the housing (2), one end of the lever arm (24,24¹) being adapted for engagement with the associated drive means (30,30¹) and the other end of the lever arm (24, 24¹) being adapted forengagement by an abutment means (28, 28¹) on the associated drive lever(8, 16) for, with the drive lever (8, 16) in its rest position, engagingthe other end of the lever arm (24, 24¹) to pivot said lever arm (24,24¹) whereby the one end thereof disengages the drive means (30, 30¹)from the ratchet mechanism (4), and, on movement of the drive lever (8,16) to a displaced position, the other end of the lever arm (24, 24¹)disengages from the abutment means (28, 28¹) and the drive means (30,30¹) move into driving engagement with the ratchet mechanism (4).
 4. Atorque wrench as claimed in claim 1 in which the lever drive means eachcomprise a fluid-operated piston-cylinder assembly (12, 20)interconnected with the other end of the associated drive lever (8, 16),extension of the piston (10, 18) of the assembly (12, 20) causingpivotal movement of the associated drive lever (8, 16) about the one endthereof from its rest position towards its fully displaced position. 5.A torque wrench as claimed in claim 4 in which the fluid supply to thepiston-cylinder assemblies (12, 20) is such that, prior to the extensionof the piston (10, 18) of one assembly (12, 20) to move the associateddrive lever (8, 16) from its rest position, the piston (18, 10) of theother assembly (20, 12) is fully retracted to hold the associated drivelever (16, 8) in its rest position.